Wrapped laminated felted monolithic combustible cartridge case

ABSTRACT

A combustible cartridge case for use with a fully telescoped round of ammunition wherein the laminated case is fabricated by wrapping thin sheets of felted combustible material. Flame penetration is moderated by applying thin films of deterrent material such as mylar between the layers to permit programmed energy release for specific tailoring of various ordnance requirements.

United States Patent Brabets et al.

[ Aug. 26, 1975 WRAPPED LAMINATED FELTED MONOLITI-IIC COMBUSTIBLECARTRIDGE CASE Inventors: Robert I. Brabets, Lombard;

Seymour Levine, Chicago, both of I11.

Assignee: The United States of America as represented by the Secretaryof the Air Force, Washington, DC.

Filed: Mar. 1, 1974 Appl. No.: 447,423

Related U.S. Application Data Continuation-impart of Ser. No, 295,077,Oct 4.

1972, abandoned.

U.S. C1. 102/38; 102/40; 102/103; 102/D1G. 1

Int. CL F42B 5/02 Field of Search 102/38, 40, 43, DIG. l,l02/100103;149/14,15,16,100

References Cited UNITED STATES PATENTS 2/1902 Maxim l02/DIG. l X

3,264,993 8/1966 DeFrics 102/DIG. l X

3,293,056 12/1966 Baker l 1011/1316. 1 X

3,316,842 5/1967 Schulz v 102/100 3,493,446 2/1970 Braun r v 102/103 X3,628,456 12/1971 Harrell.... A. l02/DIG. l X 3,677,010 7/1972 Fink102/103 3,714,047 l/l973 Marion et al. H 102/103 FOREIGN PATENTS ORAPPLICATIONS 543,739 3/1942 United Kingdom Primary Examiner-Robert F.Stahl Assistant E.\'aminerHarold Tudor Attorney, Agent, or Firm-JosephE. Rusz; Arsen Tashjian 57 ABSTRACT A combustible cartridge case for usewith a fully telescoped round of ammunition wherein the laminated caseis fabricated by wrapping thin sheets of felted combustible material.Flame penetration is moderated by applying thin films of deterrentmaterial such as mylar between the layers to permit programmed energyrelease for specific tailoring of various ordnance requirements.

5 Claims, 2 Drawing Figures WRAPPED LAMINATED FELTED MONOLITHICCONIBUSTIBLE CARTRIDGE CASE This application is a continuation-in-partof copending application Ser. No. 295,077, filed Oct. 4, 1972, and nowabandoned.

BACKGROUND OF THE INVENTION This invention relates to a wrappedlaminated felted monolithic combustible cartridge case for use with afully telescoped round of ammunition and, more particularly, theinvention is concerned with providing a combustible cartridge case whichis fabricated by wrapping thin sheets of felted combustible materialinto layers with deterrent films of mylar, cellophane, polyethylene,polyurethane or the like between the layers to moderate the flamepenetration. Increased axial stiffness is achieved which improves theprimer-igniter energy transfer efficiency.

Caseless ammunition has long been recognized as the most advantageousmeans for improving the firepower and performance of high speedautomatic weapons. The elimination of the need for extraction andejection of spent cartridge cases makes the higher firing ratespossible. Also, the caseless type ammunition is light in weight andeasier to transport and the problem of disposing of spent cartridges iseliminated.

One of the major problems in the development of caseless ammunition hasbeen the achievement of satisfactory muzzle velocity maximum pressurerequirements in weapons which use this type of ammunition. This isprimarily the result of the more or less fixed ballistic characteristicsof the cartridge propellant. The addition of more propellant onlyincreases the peak pressure and adds nothing to the improvement ofperformance of the weapon. In certain instances the peak pressure willbe increased to a point where the weapon is no longer capable of properoperation. Also, the conventional propellant used in the manufacture ofcombustible cartridge cases is inherently weak as far as its physicalproperties are concerned. Thus, it would be most desirable and a stepforward in the art to provide a combustible cartridge case wherein thepropellant could be modified to obtain a more efficient muzzlevelocity/maximum pressure ratio without adding weight to the round orsubstantially increasing the peak pressure. This would be particularlyadvantageous if it could be accomplished while at the same time addingto the physical strength of the caseless cartridge.

Accordingly, it is an object of the present invention to provide atelescoped round of caseless ammunition wherein the combustible case isfabricated by wrapping thin sheets of felted combustible material in aplurality of layers with deterrent films between the layers to moderatethe flame penetration.

Another object of the invention is to provide a combustible cartridgecase of multiple wrapped laminated construction wherein the individuallayer formulation and density are tailored to control the rate of gasgeneration.

Still another object of the invention is to provide a combustiblecartridge case fabricated by wrapping felted combustible material, suchas nitrocellulose, to form laminates. The laminates thus formed operateto increase the axial stiffness of the case allowing greater flexibilityin the use of a combustible primer by improving the primer-igniterenergy transfer efficiency.

A further object of the invention is to provide a combustible cartridgecase having a laminated configuration wherein the flexibility of aprogrammed energy release makes the concept suitable for specifictailoring to other types of ordnance requirements.

A still further object of the invention is to provide a telescoped roundof caseless ammunition wherein a monolithic combustible cartridge caseis fabricated by wrapping sheets of material into three separate layersof felted material including an inner layer, a midlayer and an outerlayer. A deterrent film is applied between adjacent layers to moderateflame penetration.

These and other objects, features and advantages will become moreapparent after considering the following detailed description taken inconjunction with the annexed drawing and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in longitudinalsection of a laminated cartridge case according to the invention showingthe plurality of laminated layers of felted material; and

FIG. 2 is a view in cross section taken along the line 2-2 of FIG. 1showing the three layers with deterrent films therebetween.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings, thehereinafter disclosed wrapped laminated felted monolithic combustiblecartridge case for use with caseless ammunition includes a fullytelescoped round of ammunition wherein a projectile 13 is positioned inthe axial bore 15 of the laminated cartridge case 17. The cartridge case17 is fabricated by wrapping thin sheets of combustible material such asnitrocellulose. In a preferred embodiment shown in FIG. 1, there arethree separate laminated layers of combustible material. The inner layer19 which is positioned closest to the projectile 13 is formed initiallyby wrapping felted combustible material to the required thickness. Athin film of deterrent 21 may be applied to the outer surface of thelayer 19 for the purpose of moderating the flame penetration to the nextadjacent layer which is called the midlayer 23. Some materials suitablefor use as the deterrent film include mylar, cellophane, polyethylenefilm and polyurethane. Mylar is a polyester film of polyethyleneterephalate resin manufactured by E. I. DuPont, Inc. Cellophane is acellulon film and polyurethane is a film of polyurethane resin. Themidlayer 23 is also formed by wrapping felted combustible material to apredetermined thickness. Another thin film of deterrent 25 made ofmaterial similar to film 21 is applied to the outer surface of themidlayer 23. An outer layer 27 is formed by wrapping the feltedcombustible material around the midlayer 23 until the final outerdiameter of the cartridge case 17 is configurated.

A combustible material suitable for use in fabricating the laminatedlayers is made by felting on a form from a water slurry ofnitrocellulose fiber, acrylic fiber, resins and stabilizer to make arough preform. This preform is subsequently molded under suitableconditions of temperature and pressure in appropriate molds to formsheets which may be furnished by trimming, if necessary. A typical finalcomposition would fall within the following:

Parts by Weight Range Nitrocellulose (12.6% N 70 55-85 Acrylic Fiber 205-35 Resin l0 Stabilizer (N,N diethylcarbamate) l Silicone Resin 4American Cyunumid: Creslan T 'JS Fibrillatable Fiber. Kraft fiber(cellulose) may be substituted for the acrylic in like amounts B. F.Goodrich, Avon Lake, Ohio: Hycar 2600x186 Dow Corning, Mcdland, Mich.:Down Corning B Silicone It can be seen that the properties of thecombustible material can be varied within a wide range to adjust theinterior ballistics of the cartridge case 17 as well as allowingeffective control of peak pressures and muzzle velocity of the round.The thickness of the deterrent films 21 and 25 can be varied between0.0005 and 0.0010 inches as a means of further controlling the rate ofgas generation by moderating the flame penetration between the layers.Also, by choosing a deterrent film of suitable composition, the flamepenetration rate can be still further controlled. Thus, by tailoring theindividual layer formulation and density within the ranges noted and bychoosing deterrent films of suitable composition and thickness, anextremely flexible energy release program can be achieved which allowsthe design to be utilized in many types of ordnance structures.

Also, it should be noted that the projectile 13 is provided with athreaded axial recess (not shown) in the center of its base portion. Aset screw 29 is threaded into the axial recess and extends aft beyondthe base of the projectile 13 to form a threaded boss thereon. A tubularigniter 31 of felted nitrocellulose is positioned in the rearwardmostpart of the axial bore 15, and includes an internally threaded forwardsection which engages the threads on the set screw 29. Within the boreof the tubular igniter 31 at the base thereof, a shoulder 33 engages aprimer 35, preferably of the combustible type, such that the primer 35is in a fixed position and the action of the firing pin (not shown) caneffectively operate to crush it on impact. Most of the forward sectionof the igniter tube 31 is filled with a standoff igniter charge of a PGblack powder. Surrounding the outer surface of the igniter tube 31,there is positioned a supplementary charge 37 which is in contact withthe inner surface of the inner layer 19 of the laminated cartridge case17.

When the telescoped round is assembled, the projectile 13 is insertedbase downward into the axial bore of the duplex cartridge case 17. Adiametral flange 39 which is the rear shoulder of the rotating band onthe projectile 13 engages a shoulder 41 on the internal surface of thelaminated cartridge case 17 and stops further downward movement. Theigniter tube 31 is then threadably attached to the set screw 29 whichhad previously been fixedly positioned on the base of the projectile 13.The igniter tube 31 is tightened in position by using a spanner-typewrench which fits into the openings 43 in the base of the igniter tube31. The operation of turning the igniter tube 31 causes the diametralflange 39 of the projectile 13 to be drawn against the shoulder 41 whilethe base portion of the igniter tube is pressed against the shoulder 45locking all of the elements in position. This procedure effectivelyloads the central portion of the igniter 31 in tension and the forwardsection through the threads are loaded in shear to produce a stresspattern which is well able to withstand ramming. At the same time, quickopening effects are achieved by the internal pressurization of theigniter tube 31 very early in the ballistic cycle.

In accordance with the invention, the laminated cartridge case 17 can beprepared by wrapping thin sheets of felted combustible material to apredetermined thickness. The finished cartridge case can be made inthree layers, the inner layer, midlayer and outer layer. Moderation ofthe flame penetration is achieved by applying deterrent films of variouscompositions and thickness to the surfaces of the laminated layers whichcontact the next adjacent layer. Although a three layer laminatedcartridge case is suggested, it should be apparent that more or lessthan three layers would be desirable under certain specific ballisticconditions. Also, the need for molded propellants is entirely eliminatedwhile at the same time a much improved structural configuration with fargreater physical strength is obtained.

In the laminated cartridge case 17, the individual layer formulation anddensity can be easily tailored to control the rate of gas generation.Also, the hereinbefore described case places less constraint on the useof a combustible primer since the increased axial stiffness improves theprimer-igniter energy transfer efficiency.

Although the invention has been illustrated in terms of a preferredembodiment thereof, the invention is not limited to this embodiment orto the preferred configuration shown. For example, it will be apparentto those skilled in the art that our invention provides a means forincreasing the muzzle velocity of the weapon without substantiallyincreasing the peak pressure by using caseless ammunition of thelaminated type. In effect, with this design, a progressive burninggeometry propellant is achieved with a corresponding increase in gunperformance. Also, it should be understood that various changes,alterations, modifications and substitutions, particularly with respectto the construction details can be made in the arrangement of theseveral elements without departing from the true spirit and scope of theappended claims.

Having thus described our invention what we claim and desire to secureby Letters Patent of the United States is:

1. A wrapped laminated felted monolithic combustible cartridge case fora fully telescoped round of ammunition comprising, in combination:

a laminated propellant charge of substantially cylindrical configurationwith an axial bore, therethrough and having a plurality of concentriclayers,

the first of said concentric layers being an inner layer comprising aseries of laminations of sheet combustible material having an insidediameter substantially equal to the outside diameter of the projectilein said telescoped round and wrapped to a predetermined thickness,

a first deterrent film on the outer surface of said first concentriclayer,

the second of said layers being a midlayer immediately adjacent theouter surface of said first deterrent film, said midlayer comprising aseries of laminations of sheet combustible material wrapped to apredetermined thickness,

a second deterrent film on the outer surface of said second concentriclayer, and

the third of said layers being an outer layer immediately adjacent theouter surface of said second denitrocellulose fiber, acrylic fiber,resins and stabilizer.

3. The laminated cartridge case defined in claim 1 wherein each of saidfirst and second deterrent films is composed of a polyester film ofpolyethylene terephalate resin.

4. The laminated cartridge case defined in claim 1 wherein each of saidfirst and second deterrent films is composed of a cellulose film.

5. The laminated cartridge case defined in claim 3 wherein the thicknessof each of said first and second polyester films of polyethyleneterephalate resin is in the range between 0.0005 and 0.0010 inches.

1. A wrapped laminated felted monolithic combustible cartridge case fora fully telescoped round of ammunition comprising, in combination: alaminated propellant charge of substantially cylindrical configurationwith an axial bore therethrough and having a plurality of concentriclayers, the first of said concentric layers being an inner layercomprising a series of laminations of sheet combustible material havingan inside diameter substantially equal to the outside diameter of theprojectile in said telescoped round and wrapped to a predeterminedthickness, a first deterrent film on the outer surface of said firstconcentric layer, the second of said layers being a midlayer immediatelyadjacent the outer surface of said first deterrent film, said midlayercomprising a series of laminations of sheet combustible material wrappedto a predetermined thickness, a second deterrent film on the outersurface of said second concentric layer, and the third of said layersbeing an outer layer immediately adjacent the outer surface of saidsecond deterrent film, said outerlayer comprising a series oflaminations of sheet combustible material wrapped to a thickness equalto the outside diameter of said cartridge case, said first and seconddeterrent films operating to moderate the flame penetration to each ofthe next adjacent layers of combustible material, thereby effectivelycontrolling the rate of gas generation to provide increased muzzlevelocity without substantially increasing the peak pressure.
 2. Thelaminated cartridge case defined in claim 1 wherein the laminations ofsheet combustible material in the plurality of layers include acomposition of felted nitrocellulose fiber, acrylic fiber, resins andstabilizer.
 3. The laminated cartridge case defined in claim 1 whereineach of said first and second deterrent films is composed of a polyesterfilm of polyethylene terephalate resin.
 4. The laminated cartridge casedefined in claim 1 wherein each of said first and second deterrent filmsis composed of a cellulose film.
 5. The laminated cartridge case definedin claim 3 wherein the thickness of each of said first and secondpolyester films of polyethylene terephalate resin is in the rangebetween 0.0005 and 0.0010 inches.